What is the primary action of mirtazapine in the body?

Mirtazapine is primarily known for its action as an antidepressant that works through a unique mechanism compared to other types of antidepressants. Its main action is to stimulate the release of norepinephrine and serotonin which occurs by antagonizing certain adrenergic receptors (specifically alpha-2 adrenergic receptors). This antagonism promotes the release of norepinephrine, which in turn activates the serotonin system, leading to an increase in serotonin levels also.

This dual action is particularly beneficial in treating conditions like major depressive disorder, as it not only enhances norepinephrine levels but also boosts serotonin, thereby improving mood and alleviating depressive symptoms. Mirtazapine does not primarily block serotonin reuptake, which distinguishes it from many other antidepressants that target serotonin reuptake inhibition as their primary mechanism. Additionally, enhancing GABA activity is not a primary action of mirtazapine but may occur as a secondary effect, while inhibiting the release of serotonin does not accurately describe its mechanism. Therefore, the option relating to the stimulation of norepinephrine and serotonin release accurately reflects the primary action of mirtazapine.